console.log('\x1b[31mdelete\x1b[0m');
let 树数组 = new  Array('红木', '栗', '杉', '橡', '枫');
for (let i in 树数组) {
    console.log(i);
}
console.log('------------')
delete 树数组[3];
for(let i in 树数组) {
    console.log(i);
}


console.log('\x1b[31mtypeof\x1b[0m');
let 我的函数 = new Function('5+2');
let 形状 = '圆';
let 大小 = 1;
let 今天 = new Date();
console.log(typeof 我的函数);
console.log(typeof 形状);
console.log(typeof 大小);
console.log(typeof 今天);
console.log(typeof true);
console.log(typeof null);
console.log(typeof 62);
console.log(typeof Math.LN2);


console.log('\x1b[31mvoid-不推荐使用\x1b[0m');
let a = void 0;
console.log(a);
console.log('---------')
function 做一些事() {
    return 42;
}
console.log(void 做一些事());
console.log('----------')
const 函数 = () => void 做一些事();
console.log(函数());
console.log('--------');
let x;
if (x === void 0) {
    console.log('x 是 undefined');
}


console.log('\x1b[31min\x1b[0m');
console.log('PI' in Math);


console.log('\x1b[31minstanceof\x1b[0m');
let 那天 = new Date(1995, 12 ,17);
if (那天 instanceof Date) {
    console.log('校验通过');
}